Fiberglass pipe insulation is sold in extremely large volume throughout the world. In more recent time, molded or extruded rigid or flexible foam pipe insulation has become a factor in the market. This foamed or microcellular pipe insulation may be of polyethylene, polypropylene, vinyl resin, polyurethane, polystyrene and related plastic materials. Usually, the blowing of the plastic is controlled to give a foam having a relatively tough, smooth integral skin which can be painted without being covered with a fabric member.
The following list of my patents indicate the nature of some of the prior art products and how they are made: U.S. Pat. Nos. 4,157,410; 4,264,388; and 4,389,270 relative to fiber glass insulation.